An answer to my question. I’d emailed to ask what ‘poor track conditions’ means, and it seems it’s a cover-all for general rail problems. I wonder if that’s a reaction to the general ribbing the train operators got to the ‘wrong kind of snow / leaves on the line’ excuses they gave years ago, as it seems to be a delicate re-wording of those announcements.

The reply said:

In most cases “poor track conditions” is used to describe lack of traction on the track and trains are unable to grip the rails causing them to slow down. This is mainly due to adverse weather conditions or leaves on the line.

It astounds me that a train weighing several tonnes can be jeopardised by a few leaves falling from the trees, which leaves me with two questions (no pun intended).

1. Did this always happen, or is it only because we now have lighter, more efficient trains that can’t call on the forces of mass and gravity to provide sufficient traction? Or,
2. Are we now such an ultra-cautious society that we daren’t do anything that invokes even a theoretical chance of danger, such as running a train at full speed on some slippery leaves?